/api/inkle/bookkeeping/entity/{entity_id}/financial_closing/{financial_closing_id}/variance_report/

Marks a closing period's variance report as generated so the FE shows View/Regenerate instead
of Generate for this row. Triggers no report computation or LLM calls itself — the FE drives those
via interactive_report/new/ (use_cached_report) and variance_explanation/ (force_regenerate)
directly.